HIV-1 infection is often complicated with neurologic disorders, but the pathogenesis of HIV-1 encephalopathy is incompletely understood. Several lines of evidence suggest that Tat (HIV-1 transactivator protein) along with inflammatory cytokines such as TNFalpha and IFNgamma released by HIV-1 infected cells contribute to HIV-1 encephalitis, ethanol has been postulated as a co-factor that adversely affects HIV-1 encephalopathy. But the effect of ethanol in the pathogenesis and progression of HIV-1 associated neurologic disorders is unclear. Epidemiological studies have resulted in conflicting results as to what role, if any, ethanol plays in HIV-1 associated neuropathogenesis. This application is in response to the RFA-AA-01-008 (Effects of alcohol on HIV Invasion Across the Blood-Brain Barrier). We isolated and cultivated human brain microvascular endothelial cells (HBMEC), which constitute the blood-brain barrier. We shoed that clinically relevant concentrations of ethanol (10-100mM) primed HBMEC for the upregulation of vascular endothelial growth factor receptor-2 (VEGFR2 or KDR), resulting in increased cytotoxicity, permeability and intracellular Ca2+ in response to Tat. These cytopathic changes of HBMEC in response to ethanol/Tat were abrogated by anti-KDR antibody. Ethanol or Tat by itself did not exhibit such effects in HBMEC. The overall aim of this application is to further characterize the priming effect of ethanol in Tat-mediated cytotoxicity, permeability, and intracellular Ca2+ in HBMEC. Specific aims are as follows: 1. To further characterize the upregulation of KDR by clinically relevant concentrations of ethanol (10-100mM) in HBMEC. 2. To examine priming effect of ethanol in Tat-mediated cytotoxicity, permeability and intracellular Ca2+ in HBMEC. 3. To investigate the mechanisms of ethanol/Tat-mediated cytopathic changes in HBMEC, i.e., nitric oxide and signaling pathways. The information derived from this proposal should enhance our understanding of the role of ethanol in HIV-1 neuropthogenesis.